1. Field of the Invention
The present invention relates to a radiation-detecting device for detecting radiation and a method of manufacturing the radiation-detecting device.
2. Description of the Related Art
In radiography, an image is obtained when radiation is applied to a subject and the radiation passing therethrough is detected by a radiation detector. In digital radiography (DR), an image is obtained by converting the detected radiation into electrical signals and digitizing the electric signal with a DR detector. To that end, in DR, a flat panel detector (FPD) which detects radiation and converts the radiation into electrical signals is usually used. The FPD includes two-dimensionally arranged photodetecting elements (e.g., photodetectors) and a scintillator layer overlying the photodetecting elements. The operation principle of the FPD is as follows: light (scintillation light) emitted from the scintillator layer irradiated with radiation is detected and is converted into electrical signals with the photodetecting elements, which are made of amorphous or polycrystalline silicon, and the electrical signals are processed into an image with digital circuitry connected to the photodetecting elements. The scintillator layer of the FPD is made of a commonly known material such as Gd2O2S:Tb prepared by doping an oxysulfide of gadolinium with terbium, which serves as a luminescent center. Alternatively, the scintillator layer can be made of CsI:Tl prepared by doping cesium iodide with thallium. In particular, an FPD containing CsI:Tl is useful in obtaining high resolution because the CsI:Tl layer is formed by vacuum vapor deposition so as to have a plurality of independent columnar crystals and therefore so-called crosstalk is reduced by a light-guiding effect in the columnar crystals.
Japanese Patent Laid-Open No. 2000-75038 discloses a radiation image sensor including a photodiode array including two-dimensionally arranged photodetectors and columnar scintillators. The columnar scintillators are disposed on the photodetectors in a one-to-one correspondence thereto and in spaces between neighboring photodetectors. The columnar scintillators which are disposed between the neighboring photodetectors are smaller in size than the columnar scintillators disposed on the photodetectors.
In Japanese Patent Laid-Open No. 2000-75038, in order to obtain the above-described configuration, columnar scintillators smaller in size than the photodetectors are uniformly formed on the photodetectors and in a space between the neighboring photodetectors. Then, the columnar scintillators disposed on the photodetectors are formed in such a manner that the small-sized columnar scintillators disposed on the photodetectors are irradiated with a laser beam so as to be fused with each other. As a result, columnar scintillators of substantially equal size to the photodetectors are disposed on each photodetector in a one-to-one relationship thereto, and columnar scintillators smaller in size are disposed between neighboring photodetectors. The technique of fusing the small columnar scintillators with each other with a laser beam, however, damages the scintillators disposed on the photodetectors and therefore can be detrimental to image quality.